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In this work, different previously unexplored features are investigated for the radiation performance of linear phased arrays based on printed-circuit leaky-wave antennas for microwave and millimeter-wave applications. By means of a rigorous modal analysis in the unit cell based on the spectral-domain approach, we have considered the beam-scanning properties of microstrip leaky-wave arrays in terms of spatial harmonics, as a function of both the phase shift and the spacing between the radiating microstrip lines. We have thus found and interpreted in a consistent way various original characteristics, such as transition regions between leaky-wave and surface-wave regimes, and the occurrence of spurious radiation (grating lobes) in largely spaced arrays related to the presence of new, additional complex improper modes. Numerical full-wave simulations of the radiation patterns for realistic configurations of microstrip arrays confirm the theoretical predictions made on the basis of the modal properties of the involved leaky waves.
Date of Publication: Dec. 2003